The present invention relates, according to an aspect thereof, to a method for providing an electrical connection arrangement between a first member and a second member, wherein said first member being made of electrically conductive material provided with a coating layer, and wherein said electrical connecting arrangement comprising a fastening element for connecting said first and second members. The present invention also relates, according to an aspect thereof, to an electrical connection arrangement comprising a first member, a second member, and a fastening element, wherein said first member being made of electrically conductive material provided with a coating layer.
Electronic equipment, such as electronic control units arranged on different members in for example a vehicle require good earth connections between the different members for proper and reliable functioning, partly due to the diminishing signal levels used in modern electronic equipment. High quality earth connections provide low electrical resistance between the different members, thus assuring substantially the same electrical reference potential over the entire electrical system. This is particularly demanding in vehicle applications where no physical ground connection is available. Instead, the bodywork or chassis of the vehicle serves as zero potential voltage reference and as return path for the entire electrical system of the vehicle.
Prior art solutions for providing earth connection between for example an electronic product mounted and connected to an separate electrically conducting support structure and chassis main ground rely mainly on studs welded to the separate members, which studs were covered during painting not to become coated for maintained electrical contact. Subsequent interconnection of the support structure and chassis ground is often made by braided earth leads secured to the welded studs. This solution has the disadvantage of high manufacturing costs, poor corrosion resistance and low flexibility with respect to mounting of addition equipment after sales due to lack of studs.
Another prior art disclosed in WO 2005/025005 shows a ground connection based on a separate grounding element that is secured to a hole in the chassis main ground, wherein the grounding element is adapted to receive a ground cable for earth connection with a support structure. This solution however has the disadvantage of not providing a reliable earth connection, and suffering from risk of corrosion.
There is thus a need for an improved electrical connection between different members removing the above-mentioned disadvantages.
It is desirable to provide an inventive method for providing an electrical connection arrangement between a first member and a second member where the previously mentioned problems are partly avoided. According to an aspect of the invention, a first member is made of electrically conductive material provided with a coating layer, and wherein said electrical connecting arrangement comprising a fastening element. The method further comprises the steps of providing said first member with a first hole, arranging a sleeve in said first hole of said first member, such that said first member becomes electrically connected with said sleeve, coating an area of said first member comprising said sleeve, and inserting said fastening element into said sleeve and through the first member, and engaging said fastening element with said second member, such that the fastening element becomes abutted against an uncoated surface portion provided on said sleeve to electrically connect said sleeve with said fastening element, and such that said fastening element becomes electrically connected to said second member.
According to another aspect of the invention, an electrical connection arrangement comprising a first member, a second member, and a fastening element is provided, wherein said first member being made of electrically conductive material provided with a coating layer and a first hole, wherein a sleeve is arranged in said first hole prior to application of said coating layer, such that said first member is electrically connected to said sleeve, said fastening element is arranged to abut an uncoated surface portion of said sleeve to provide electrical contact between said sleeve and said fastening element, and said fastening element is engaged with said second member, such that said fastening element is electrically connected to said second member.
Aspects of the invention provide a cost-efficient and flexible solution for providing one or several earth connections between a first member in form of for example a bolted-on support structure and a second member in form of for example a chassis main ground. Attachment of the sleeve can be made in a fast and simple manner and suitable for automated manufacturing, and after complete installation, good corrosion resistant is provided by means of the coating layer of the first member in combination with a corrosion-averse material of the sleeve. The uncoated surface portion of the sleeve is arranged to be in electrical contact with the fastening element, and eliminates thus any need of for example a toothed washer applied for penetrating a coating layer of the sleeve.
The contact surface between the sleeve and first member is also significantly increased by means of the flange of the sleeve, which flange is arranged to abut the surface of the first member, thus minimizing electrical resistance between the first member and the sleeve. Electrical connection between the sleeve and the second member is subsequently fast and efficiently accomplished by means of the fastening element that is arranged to abut the sleeve and to engage the second member, and to electrically interconnect these parts.
Finally, the electrical connection arrangement apart from providing an earth connection also provides a rigid and reliable mechanical connection between the first and second members, thus largely removing the need for other assembly means for this purpose.
The method for providing an electrical connection arrangement advantageously further comprises the step of realising the electrical connection between said fastening element and said second member by means of threads of the fastening element, or by means of welding, soldering or riveting the fastening element to said second member. A threaded connection is a cost-effective and flexible method of attachment that also reliably abuts the fastening element against the sleeve in a simple manner.
The method for providing an electrical connection arrangement advantageously further comprises the step of providing said second member with a second hole, and coating an area of said second member comprising said second hole. This provides simplified attachment of the fastening element, such as the use of a self-tapping threaded fastening element, or forming of threads during a separate method step.
The method for providing an electrical connection arrangement advantageously further comprises the step of providing the fastening element with a head and a threaded shank, and realising the electrical connection between said threaded shank and said second member by providing said threaded shank with threads that are configured to penetrate the coating layer within said second hole, and to form threads within said second hole of said second member. This subject-matter thus provides a fast, reliable, corrosion resistant and efficient way of assembling the electrical connection arrangement.
The method for providing an electrical connection arrangement advantageously further comprises the step of providing the fastening element with a head and a threaded shank, and realising the electrical connection between said threaded shank and said second member by forming threads within said second hole of said second member, covering said threads of said second hole prior to coating of said second member with a first cover, and subsequently removing said first cover to provide a coated second member having a second hole provided with uncoated threads. This method represents an alternative method for realising threads in said second hole of the second member that may be preferred depending on material parameters, coating parameters, manufacturing, and the like.
The step of arranging said sleeve in said first hole of said first member method advantageously comprises arranging a flange of said sleeve on a rear side of said first member facing said second member. Preferably, the flange abuts said rear side and is secured thereto by means of welding. The flange may be arranged to function as distance member between the first and second members in joined configuration, and the length of the sleeve of the sleeve may preferably be selected such that an end surface of the sleeve protrudes a certain distance beyond the front surface of the first member, such that the fastening element abuts said end surface during engagement of said fastening element. Furthermore, by providing the flange on the rear surface, there is no risk that weld spatter will negatively affect the electrical connection quality between the fastening element and the sleeve, which could be the case if the fastening element would abut the flange.
The step of arranging said sleeve in said first hole of said first member method advantageously comprises arranging the flange of said sleeve on a front side of said first member facing away from said second member. One advantage of this configuration is that the length of the sleeve may be easily adapted, and that the part of sleeve that is protruding on the rear side of the first member may be arranged to function as a distance member having a large freedom of selectable parameters. The electrical contact surface between the fastening element and the sleeve is also increased, assuring a good electrical connection there between.
The method for providing an electrical connection arrangement advantageously further comprises the step of providing adhesive material between said first and second members. The adhesive material improves joining of said first and second members, and efficiently seals the contact area and reduces risk of corrosion.
Advantageously, said sleeve is arranged to protrude a certain distance beyond a rear surface of the first member facing the second member, and to form a spacing element between said first and second members. Hereby, the first and second members may be safely mounted with a distance in-between, and over-compression of any adhesive material arranged between the members may be prevented. Either the flange part or the sleeve part of the sleeve will protrude depending on how the sleeve is arranged within the first hole.
The method step of providing an uncoated surface portion on said sleeve advantageously involves covering said surface portion with a second cover prior to coating said first member, and subsequently removing said second cover after coating to provide a coated first member having said uncoated surface portion. Hereby, a high quality abutment surface is provided on the sleeve, substantially without coating traces.
The method for providing an electrical connection arrangement advantageously further comprises the step of selecting the size of said second cover such that said uncoated surface portion is limited to said sleeve. In case the flange of the sleeve abuts a front surface of said first member, the size of said second cover is selected such that said coating layer covers a rim and a potential weld area of said flange, and extends a certain distance towards the centre of said flange. In case the flange of the sleeve abuts a rear surface of said first member, the size of said second cover is selected such that said coating layer extends onto the protruding sleeve of the sleeve. In either case, the coating layer is arranged to extend onto the sleeve and thus to completely seal the first member, such that the likeliness of moisture reaching uncoated areas of the first member is reduced. In case the sleeve is welded to the front surface of the first member, the coating may advantageously cover also the weld area of the sleeve, thus reducing the likelihood of corrosion thereof.
First and/or second cover may advantageously be formed of a plastic plug that is inserted into the sleeve during coating thereof. Preferably, said plug is made of silicone to assure good cover performance.
The method for providing an electrical connection arrangement comprising the step of providing an uncoated surface portion on said sleeve advantageously involves mechanically, thermally or chemically removing the coating layer on said sleeve corresponding to said surface portion after coating to provide a coated first member having said uncoated surface portion. This process step provides a fast and efficient solution for providing said uncoated surface portion, whereby no cover needs to be handled during the coating process, which cover may otherwise fall of. Moreover, the size, shape and location of the uncoated surface portion may be easily adapted at the end of the manufacturing process.
The method for providing an electrical connection arrangement advantageously further comprises the step of securing said sleeve in said first hole of said first member by welding, riveting or press-fitting said sleeve with said first member. Most important is that the fastening solution provides good electrical contact between the sleeve and first member. The electrical contact may be further improved by providing the sleeve of the sleeve with exterior ribs or projections that engage the inner surface of the first hole in the first member.
Advantageously, said sleeve and/or said fastening element are made of a corrosion resistant material, in particular stainless steel, or are provided with a corrosion resistant coating. Some areas of the sleeve and fastening element will remain uncoated after complete assembly, and may therefore be exposed to a corrosive environment. Corrosion resistance is therefore of benefit.
Advantageously, said coating layer is powder coating that preferably is applied in a painting process.
Advantageously, electronic equipment, such as micro computers and relays, is attached, and provided with a ground connection to said first member, and said second member forms part of a electrically conducting frame structure of a device, in particular a vehicle, wherein said electrical connection arrangement serves to provide said electronic equipment with at least one earth connection to said frame structure, preferably two separate earth connections to said frame structure, and more preferably at least three separate earth connections to said frame structure. Each of the inventive earth connections is provided without the use of earth cables and provides thus a reliable ground connection with low electrical resistance, thus satisfying the current demands earth connections of low signal voltage electrical control units.